A nearly complete juvenile skull of the marsupial Sparassocynus derivatus from the Pliocene of Argentina, the affinities of “sparassocynids”, and the diversification of opossums (Marsupialia; Didelphimorphia; Didelphidae)

Beck, RMD ORCID: https://orcid.org/0000-0002-7050-7072 and Taglioretti, ML 2019, 'A nearly complete juvenile skull of the marsupial Sparassocynus derivatus from the Pliocene of Argentina, the affinities of “sparassocynids”, and the diversification of opossums (Marsupialia; Didelphimorphia; Didelphidae)' , Journal of Mammalian Evolution , pp. 1-33.

[img]
Preview
PDF - Published Version
Available under License Creative Commons Attribution 4.0.

Download (13MB) | Preview
[img] PDF - Accepted Version
Restricted to Repository staff only

Download (5MB) | Request a copy

Abstract

“Sparassocynids” are small, carnivorously-adapted marsupials known from the late Miocene and Pliocene of South America, thought to be relatives of living didelphid opossums but of otherwise uncertain phylogenetic relationships. Here, we describe a nearly complete juvenile skull of the “sparassocynid” Sparassocynus derivatus, from the Pliocene (~5-3 million years old) Chapadmalal Formation, Argentina. It provides new information on the morphology of Sparassocynus, including the deciduous dentition, and (together with previously collected specimens) allows reinterpretation of the derived auditory region of “sparassocynids.” The new specimen also exhibits several distinctive apomorphies characteristic of Didelphidae and of subclades within the family. Undated Bayesian phylogenetic analysis of a total evidence dataset (132 craniodental characters, 7.3 kb of DNA sequence data from five nuclear genes) places “sparassocynids” within the didelphid genus Monodelphis, whereas “tip-andnode” dating analysis of the same dataset with an Independent Gamma Rates (IGR) clock model places them as sister to Monodelphis, showing that temporal information influenced the resultant topology. We conclude that “sparassocynids” warrant tribal separation only, as Sparassocynini new rank. Based on our dated phylogeny, we also provide a revised scenario for didelphid diversification. Crown-clade didelphids probably originated close to the Oligocene-Miocene boundary. We agree with previous proposals that the appearance of carnivorously-adapted didelphids in South America during the late Miocene, including sparassocynins, is likely related to a decline in diversity of the sparassodonts at this time, and that the disappearance of these carnivorously-adapted didelphids at the end of the Pliocene may have been due to the arrival of placental carnivorans, such as mustelids, from North America.

Item Type: Article
Schools: Schools > School of Environment and Life Sciences > Ecosystems and Environment Research Centre
Journal or Publication Title: Journal of Mammalian Evolution
Publisher: Springer
ISSN: 1064-7554
Related URLs:
Funders: National Science Foundation, Australian Research Council, Santander Travel Award
Depositing User: R Beck
Date Deposited: 05 Jun 2019 08:57
Last Modified: 08 Aug 2019 13:00
URI: http://usir.salford.ac.uk/id/eprint/51482

Actions (login required)

Edit record (repository staff only) Edit record (repository staff only)

Downloads

Downloads per month over past year